Widespread contamination of human milk by polychlorinated biphenyls (PCBs) and 1,1-(p-chlorobiphenyl)-2,2-dichloroethane (DDE, a metabolite of the pesticide DDT) is well documented, but illnesses resulting from such exposure to nurslings are essentially unstudied. This project involves: (1) development of sampling and PCB/DDE analysis methods for breast milk and other tissues and fluids that are reliable, reproducible, and contaminant free; (2) establishment and follow-up of a cohort of children for whom analyzed samples of milk and clinical data are available; (3) development of alternate methods of chemical analysis that are faster or cheaper than gas liquid chromatography; (4) evaluation of the children for specific outcomes thought to be related to DDE/PCB exposure; (5) data cleanup, editing and analysis.